Method of testing flammability of fibers

ABSTRACT

Flammable fibers are blended and/or twisted with fibers which are substantially less flammable and of relatively high melting point, and subsequently knit or woven into a fabric. The fabric is stretched across and along a semicircular bifurcated nonflammable frame, and ignited on one end. Burning characteristics of the fibers being tested can then be observed without the adverse burn- irregularity otherwise caused by melting or shrinkage of the fibers away from heat and flame.

United States Patent [56] References Cited UNITED STATES PATENTS 12/1945Hubert.......v.................

Primary Examiner-.lames J. Gill [72] Inventors EugeneL.Ringwald MitchellT. Burden. Apex; Henry L. King, 2 391 161 Cary, all of, N.C. Appl. No.771,406 Filed [45] Patented June 1, 1971 [22] Oct. 29, 1968 AssistantExaminer-Herbert Goldstein Attorneys-Thomas Y. Await, Jr. and Robert L.Broad, Jr. [73] Assignee Monsanto Company St. Louis, Mo.

ABSTRACT: Flammable fibers are blended and/or twisted with fibers whichare substantially less flammable and of relatively high melting point,and subsequently knit or woven into FIBERS a fabric. The fabric isstretched across and along a semicircuignited on one end.

9 Claims, 1 Drawing Fig.

lar bifurcated nonflammable frame, and Burning characteristics of the t:

bers being tested can then be 73/15 ....G0ln 25/00 [50] Field of [51]1nt.Cl.............

observed without the adverse bumirregularity otherwise caused by meltingor shrinkage of the fibers away from heat and flame.

PATENTEU JUN 1 197:

.INVENTORS E. L. RINGWALD M. T. BURDEN j H.L. KING ATTORNE METHOD OFTESTING FLAMMABILITY OF FIBERS BACKGROUND OF THE INVENTION Thisinvention relates to a method of testing the flammabilitycharacteristics of fibers, filaments, and the like.

Various devices and procedures are known for measuring the flammabilityof sheeted material including plastics, fabrics, carpets, and the like.Devices include mechanical and electrical means and combinations thereofto provide in a series of samples, relative measurements of burningspeed, heat of combustion, etc. by varying the application of heat, evenby providing for testing at various slopes of the film from thevertical.

It is well known that a sheeted material will burn most rapidly in thedirection of a draft and that the draft caused by burning will, unlessdiverted, direct itself vertically. Samples of sheeted material may betested for flammability while stretched in a vertical position or at anyangle from the vertical; and variances as between different types ofmaterials will be noted.

Prior art procedures and devices for testing flammable fibers andfilaments or fabrics comprised essentially of flammable fibers orfilaments have proved unsatisfactory not only because the burningpositions and position ranges of samples failed to reflect subtledifferences between samples, but also because many of the fibers have atendency to shrink away from the heat of the flame, and therefore do notignite or burn evenly or reproducibly; and known testing devices havebeen designed for relatively nonflammable fabrics or for those that burnrapidly.

There is thus a need for a testing method which will permit theobservation of the full range of flammability characteristics of fiberswithout the "shrinking away" effect, which, by its very nature,precludes uniformity of testing results among identical samples.

SUMMARY OF THE INVENTION It is an objectof this invention to provide amethod of testing the flammability characteristics of fibers without thedetrimental effects of the shrinking characteristics of the fibers.

It is another object of this invention to provide a test fabric whichcan be used for evaluating the flammability characteristics of flammablefibers included in the test fabric.

Briefly, the objects of this invention are accomplished by blendingfibers to be tested with less flammable fibers of high melting point andknitting or weaving the fibers into a test fabric. The test fabric canthen be ignited, and the speed of burning, and the propensity to burnunder various conditions can be observed in a testing device which holdsthe test fabric strip in an arclike position.

Other objects and advantages of this invention will become apparent fromthe following detailed description read in conjunction with the appendeddrawing in which:

The FIGURE is a perspective view of one device in which the test fabricof this invention may be ignited and observed in accordance with themethod of this invention.

The term fiber as used herein includes filaments, threadlines and thelike.

Fibers and filaments suitable for testing in accordance with the instantinvention include those made from thermoplastic fiber-forming polymerswhich are formed by known techniques including melt extrusion, wetspinning processes and dry spinning processes. As examples offiber-forming synthetic polymers which are included may be mentionedpolyethylene; polypropylene, polyurethane; copolymers of vinyl acetateand vinyl chloride; the copolymers of vinylidene chloride and a minorproportion of mono-olefinic compounds copolymerizable therewith, such asfor example, vinyl chloride; homopolymers of acrylonitrile, copolymersof acrylonitrile and a minor proportion of at least one monoolefiniccompound copolymerizable therewith and polymer blends containingcombined acrylonitrile in a major proportion; copolymers of vinylchloride and acrylonitrile; linear polyesters of aromatic dicarboxylicacids and dihydric compounds, such as polyethylene terephthalate; linearpolycarbonamides, such as for example, polyhexamethylene adipamide,polyhexamethylene sebacamide; polymeric monoamino monocarboxylic acidsor their amide-forming derivatives, such as polymeric 6-aminocaproicacid; and other fiber-forming polymers. Also contemplated are mixturesof such fiberforming synthetic polymers.

Included among the less flammable fibers suitable for supporting fibersin the practice of this invention are the preferred glass fibers andasbestos fibers. Glass fibers are most practical in terms of versatilityand economy. Although there is some shrinkage of glass fibers fromflame, the fibers are stable enough to hold the test fibers during thecourse of burning. Any fiber which is substantially less flammable andwith a higher melting point than fiber being tested will serve as asatisfactory matrix for the fiber being tested.

In the preparation of these test fabrics, there are no criticalproportions as between the test fibers and the supporting fibers. Wehave found that test fabrics made up with as little as 10 percent of thesupporting fibers suffice to accomplish the purpose of the blending. Themanner of blending or incorporation of the supporting fibers into thefabric is immaterial. Conventional blending techniques may be used; orthe supporting fibers may be twisted with the test fibers. Combinationsof twisting and conventional blending may also be used. The structuralfeatures of the test fabric are unimportant, and any conventional methodof making a fabric, including knitting or weaving, can be used. It isimportant, of course, that all test samples be prepared in the samemanner. Any variation in the blend or structure as between test sampleswill lead to variations in testing results not attributable to thecharacteristics of the test fibers.

A strip of the test fabric is held in a semicircular position,preferably by stretching along a semicircular frame. The ends of thesemicircle should be at a position where the radius is horizontal. Whenone end of the test fabric is ignited, the direction of flame is atfirst vertical. As. the flame proceeds upward, the direction approachesthe horizontal. As it descends, it approaches the vertical again. Thespeed of the flame and the distance it progresses is measured as againstother samples.

Referring now in detail to the drawing, there is shown bifurcatedsemicircular frame 1 with mounting frame 2 on base 3. The bifurcations23 of frame 1 are graduated in terms of degrees along the arc. Sheetedmaterial Sample 4 is held in place between and along the bifurcations 23of frame 1 by nonflammable flexible straps 5 which are permanentlyaffixed at the juncture 8 of frame 1 and frame-mounting means 2 by aspring latch 9. The relative positions of straps 5 are maintained, whenthe straps are removed by bar 10, which is permanently affixed to theremovable ends of straps 5, and for which is provided recess 11 inframe-mounting means 2. Gas jet nozzle 12 is affixed to the end oftubing 16 which is mounted on rotatable control rod 13 equipped withhandle 14. The gas jet is provided with a flexible gas supply hose 15which feeds tubing 16 through a hollowed portion of rod 13. Tubing 16 isprovided with a stop 17 which is affixed to frame-mounting means 2 andfurnishes a finite stopping point for the jet when it approaches thesample ignition position. The testing frame is mounted in a cabinethaving a hinged top 18 and a cabinet base 19. Cabinet base 19 isprovided with gas ingress perforations 20. Top 18 is provided with gasexhaust vents 21 and transparent observation plate 22.

ln the operation of this device, spring catch 9 is released and straps 5are pulled away from frame 1 whereupon the remains of a burnt sample areremoved and a fresh sample of a woven or knitted blend of test fibersand supporting fibers is placed across and along frame 1. Hooks areprovided at juncture 7 (not shown) to hold one end of the sample inplace, while straps 5 are again fastened. The gas supply is turned onand gas jet 12 is ignited. Cabinet top 18 closed. Handle 14 is rotatedrapidly in a clockwise direction until jet support v rests against stop17. The jet is now in position to ignite the sample. Stopwatch timing iscommenced when gas jet support 16 hits stop 1?. Depending upon thenature of the sample being tested. readings are taken at uniformgraduations along the degree scale on frame 1. The point at whichburning stops is also recorded.

EXAMPLE Continuous filament poly(ethylene terephthalate) of about 100denier was simultaneously plied and twisted about 4 or 5 twists per inchwith glass fiber of approximately the same diameter as the polyestercontinuous filament. The plied and twisted filament was knitted on acircular knitting machine at about 34 inches per course into 3-inchdiameter tubing. The knitted tubing was scoured to remove any oildeposited during the knitting operation, rinsed, and dried in an oven atabout 100 C. The dried tubing was slit and cut into 18-inch by 3- inchsections and returned to the oven for 2 hours prior to testing. Cutsections were removed from the oven one at a time, mounted in thesemicircular tester and the rate of burning was determined. A %-inchlong gas flame was impinged on the fabric for 3 seconds at the angle ofthe tester. Timing of the burning was begun when the flame first touchedthe fabric. As burning of the fabric continued, times were recorded atwhich the flame front passed 90, 120, 150, and 180 angles of the tester.Results obtained on five observations with this knit fabric were foundto be very reproducible as shown from the following:

TABLE I.-3 SECOND IMPIEISMENTHODERATE TIGHT- [Burning Time, (Seconds)for each of Repeat Samples] 1 2 3 4 5 Average lt is understood that theexample given in the specification is not meant to be limitive; the testdevice shown is only one which may be used in accordance with the methodof this invention; and that the invention itself may be modified in manydetails.

What we claim is:

l. A method for testing the relative flammability of test fiberscomprising:

1. blending said test fibers in a uniform and predetermined manner withsupporting fibers which are substantially less flammable than said testfibers and which have a substantially higher melting point than saidtest fibers;

2. fabricating in a uniform and predetermined manner test samples ofsaid blended fibers;

3. igniting said test samples; and I 4. timing the burning rate of saidtest samples, thereby determining the relative flammability of said testfibers.

2. The method of claim 1 wherein said test sample is held in asemicircular position so that burning may proceed along an arc.

3. The method of claim 1 in which the test sample contains at leastabout 10 percent of supporting fibers which are substantially lessflammable.

4. The method of claim 1 wherein said supporting fibers are glassfibers.

5. The method of claim 1 wherein said supporting fibers are asbestosfibers.

6. The method of claim 1 wherein said tested fibers are thermoplasticfibers.

7. The method of claim 1 in which said test sample is stretched alongand across a bifurcated nonflammable frame.

8. The method of claim 7 wherein said bifurcated frame is semicircularand wherein the radii of said frame at the ends thereof aresubstantially horizontal.

9. The method of claim 7 wherein oxidization is controlled by performingthe test within a cabinet having means for regulating ingress and egressof gas supporting the oxidization.

2. fabricating in a uniform and predetermined manner test samples ofsaid blended fibers;
 2. The method of claim 1 wherein said test sampleis held in a semicircular position so that burning may proceed along anarc.
 3. The method of claim 1 in which the test sample contains at leastabout 10 percent of supporting fibers which are substantially lessflammable.
 3. igniting said test samples; and
 4. timing the burning rateof said test samples, thereby determining the relative flammability ofsaid test fibers.
 4. The method of claim 1 wherein said supportingfibers are glass fibers.
 5. The method of claim 1 wherein saidsupporting fibers are asbestos fibers.
 6. The method of claim 1 whereinsaid tested fibers are thermoplastic fibers.
 7. The method of claim 1 inwhich said test sample is stretched along and across a bifurcatednonflammable frame.
 8. The method of claim 7 wherein said bifurcatedframe is semicircular and wherein the radii of said frame at the endsthereof are substantially horizontal.
 9. The method of claim 7 whereinoxidization is controlled by performing the test within a cabinet havingmeans for regulating ingress and egress of gas supporting theoxidization.